PavaniRaghunath
VeritasPrepKarishma
The probability of selecting 6 and leaving 2 such that 1 is white and the other blue is the same as the probability of selecting 2 such that one is white and the other blue while 6 are remaining.
Hello VeritasPrepKarishma, can you explain how this is the same.
Let us try to make this simpler. If the question had instead asked:
"A bag contains 3 blue and 5 white marbles. One by one, marbles are drawn out randomly until only ONE is left in the bag. What is the probability that it is blue?"
We can say that there are two equivalent ways of going about this:
1. We take out 7 marbles and leave one in the bag.
2. We take out one and leave 7 in the bag.
These two operations are equivalent. After all, we are randomly separating one marble from the other seven. Hence, these two experiments will yield the same probability.
You can now extend this to the case where 2 marbles need to be separated from the rest.